Berkeley - Although what to do with the almost 400,000 wasteland sites in the United States now occupied by abandoned warehouses, derelict industrial sites and the like seems a staggering problem, a University of California, Berkeley, professor of landscape architecture and city planning says there are solutions.

City planners need to make more efficient use of land and other resources and explore ways to recycle declining or derelict resources, says Michael Southworth in his working paper, "Wastelands in the Evolving Metropolis."

"It is far easier to throw something away than to find a new use for it. Yet to achieve more sustainable cities, it will be necessary to begin to deal with the enormous waste landscapes we produce," he writes in the paper recently released by UC Berkeley's Institute for Urban & Regional Development.

Many of America's inner city "brownfields" - waste sites that account for five to 10 percent of the nation's metropolitan land area and occupy an estimated 38,000 locations in California alone - can be recycled for new uses, Southworth suggests.

As examples, he cites the Massachusetts Bay Transportation Authority's transformation of a long unused rail corridor into a linear park, and innovative waste treatment ponds in Arcata, Calif., that converted a derelict lumber mill and railroad into a wildlife sanctuary, recreational area and salmon ranch.

Even oil fields have been reclaimed as open space in Whittier, Calif., and industrial buildings are now frequently converted to studios and apartments in SoHo (South Houston) and SoMa (South of Market, San Francisco), Southworth says.

Many urban wastelands show great promise for new uses, thanks to waterfront or other locations that offer easy transportation access and sometimes stunning views, he says. Others, however, do not. Southworth says the abandoned missile silos and contaminated chemical factory properties may be best left as monuments to waste.

He cautions, however, that while automobile-dominated suburbs may waste land, they lack enough true wasteland. "They lack the wild waste spaces, the transitional zones, the 'cracks' of the old central cities," he writes. "Outdoor spaces for adventure and exploration away from public scrutiny are notably lacking."

Some wasteland is good, even necessary for future adaptability, Southworth says. Over time, he says, some acquire a special aesthetic and emotional appeal and without them the world would be "sterile and oppressive."

"Managing the wasting of places is a major responsibility of urban design and planning in both the city center and at the edge," says Southworth.